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/*
* Copyright (C) 2013 The Android Open Source Project
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.android.inputmethod.keyboard.internal;
import com.android.inputmethod.annotations.UsedForTesting;
import android.util.Log;
import java.util.Arrays;
/**
* Utilities for matrix operations. Don't instantiate objects inside this class to prevent
* unexpected performance regressions.
*/
@UsedForTesting
public class MatrixUtils {
private static final String TAG = MatrixUtils.class.getSimpleName();
public static class MatrixOperationFailedException extends Exception {
private static final long serialVersionUID = 4384485606788583829L;
public MatrixOperationFailedException(String msg) {
super(msg);
Log.d(TAG, msg);
}
}
/**
* A utility function to inverse matrix.
* Find a pivot and swap the row of squareMatrix0 and squareMatrix1
*/
private static void findPivotAndSwapRow(final int row, final float[][] squareMatrix0,
final float[][] squareMatrix1, final int size) {
int ip = row;
float pivot = Math.abs(squareMatrix0[row][row]);
for (int i = row + 1; i < size; ++i) {
if (pivot < Math.abs(squareMatrix0[i][row])) {
ip = i;
pivot = Math.abs(squareMatrix0[i][row]);
}
}
if (ip != row) {
for (int j = 0; j < size; ++j) {
final float temp0 = squareMatrix0[ip][j];
squareMatrix0[ip][j] = squareMatrix0[row][j];
squareMatrix0[row][j] = temp0;
final float temp1 = squareMatrix1[ip][j];
squareMatrix1[ip][j] = squareMatrix1[row][j];
squareMatrix1[row][j] = temp1;
}
}
}
/**
* A utility function to inverse matrix. This function calculates answer for each row by
* sweeping method of Gauss Jordan elimination
*/
private static void sweep(final int row, final float[][] squareMatrix0,
final float[][] squareMatrix1, final int size) throws MatrixOperationFailedException {
final float pivot = squareMatrix0[row][row];
if (pivot == 0) {
throw new MatrixOperationFailedException("Inverse failed. Invalid pivot");
}
for (int j = 0; j < size; ++j) {
squareMatrix0[row][j] /= pivot;
squareMatrix1[row][j] /= pivot;
}
for (int i = 0; i < size; i++) {
final float sweepTargetValue = squareMatrix0[i][row];
if (i != row) {
for (int j = row; j < size; ++j) {
squareMatrix0[i][j] -= sweepTargetValue * squareMatrix0[row][j];
}
for (int j = 0; j < size; ++j) {
squareMatrix1[i][j] -= sweepTargetValue * squareMatrix1[row][j];
}
}
}
}
/**
* A function to inverse matrix.
* The inverse matrix of squareMatrix will be output to inverseMatrix. Please notice that
* the value of squareMatrix is modified in this function and can't be resuable.
*/
@UsedForTesting
public static void inverse(final float[][] squareMatrix,
final float[][] inverseMatrix) throws MatrixOperationFailedException {
final int size = squareMatrix.length;
if (squareMatrix[0].length != size || inverseMatrix.length != size
|| inverseMatrix[0].length != size) {
throw new MatrixOperationFailedException(
"--- invalid length. column should be 2 times larger than row.");
}
for (int i = 0; i < size; ++i) {
Arrays.fill(inverseMatrix[i], 0.0f);
inverseMatrix[i][i] = 1.0f;
}
for (int i = 0; i < size; ++i) {
findPivotAndSwapRow(i, squareMatrix, inverseMatrix, size);
sweep(i, squareMatrix, inverseMatrix, size);
}
}
/**
* A matrix operation to multiply m0 and m1.
*/
@UsedForTesting
public static void multiply(final float[][] m0, final float[][] m1,
final float[][] retval) throws MatrixOperationFailedException {
if (m0[0].length != m1.length) {
throw new MatrixOperationFailedException(
"--- invalid length for multiply " + m0[0].length + ", " + m1.length);
}
final int m0h = m0.length;
final int m0w = m0[0].length;
final int m1w = m1[0].length;
if (retval.length != m0h || retval[0].length != m1w) {
throw new MatrixOperationFailedException(
"--- invalid length of retval " + retval.length + ", " + retval[0].length);
}
for (int i = 0; i < m0h; i++) {
Arrays.fill(retval[i], 0);
for (int j = 0; j < m1w; j++) {
for (int k = 0; k < m0w; k++) {
retval[i][j] += m0[i][k] * m1[k][j];
}
}
}
}
/**
* A utility function to dump the specified matrix in a readable way
*/
@UsedForTesting
public static void dump(final String title, final float[][] a) {
final int column = a[0].length;
final int row = a.length;
Log.d(TAG, "Dump matrix: " + title);
Log.d(TAG, "/*---------------------");
final StringBuilder sb = new StringBuilder();
for (int i = 0; i < row; ++i) {
sb.setLength(0);
for (int j = 0; j < column; ++j) {
sb.append(String.format("%4f", a[i][j])).append(' ');
}
Log.d(TAG, sb.toString());
}
Log.d(TAG, "---------------------*/");
}
}
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